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In this paper, we have reported on improved titanyl phthalocyanine (TiOPc) thin film transistor (TFT) performance utilizing an α,α′-dihexylsexithiophene (DH-α6T) submonolayer. By the detailed XRD and AFM analysis, highly ordering α-TiOPc thin films could be deposited on SiO2/Si substrates modified by a DH-α6T submonolayer. Organic TFT with a TiOPc/ DH-α6T bilayer as active layers realized high mobility of 2.45 × 10−1cm2/V s, which is about 100 times greater than that of TiOPc single layer device. [ABSTRACT FROM AUTHOR]

Abstract: Flexible pentacene thin film transistors were fabricated and characterized with a hydroxyl-free and amorphous low-k cyclo-olefin polymer (COP) as a gate dielectric. The maximum processing temperature was 60°C. The spin-coated COP thin films had excellent electrical insulating properties, and the pentacene TFTs showed negligible current hysteresis, a field-effect mobility of 1.60cm2 /Vs, a subthreshold swing of 0.56V/decade and an on/off ratio of>106. Furthermore, a small threshold voltage shift below 1.83V was obtained despite unpassivation of the pentacene layer after a gate bias stress of 104 s. These excellent air stabilities were attributed to the insulator with hydroxyl-free and low water absorbency. [Copyright &y& Elsevier]

Abstract: We report the effects of thermal annealing on structure, morphology and electrical properties of fluorinated copper phthalocyanine (F16CuPc)/α-sexithiophene (α6T) heterojunction thin films. The morphology and structure of the thin films were examined by atomic force microscopy and X-ray diffraction techniques. The thermal annealing significantly improved α6T molecular ordering although F16CuPc molecular was slightly disordered in the thermal annealing process. The smallest full width of half maximum of the 200 diffraction lines was gained at the thermal annealing temperature of 150°C. Similarly, ambipolar performance of the F16CuPc/α6T heterojunction transistor could be improved by the thermal annealing. At the thermal annealed temperature of 150°C, the ambipolar device achieved high-performance with field-effect hole and electron mobilities of 8.84×10−3 cm2 V−1 s−1 and 1.00×10−2 cm2 V−1 s−1, respectively. [Copyright &y& Elsevier]

Abstract: We have investigated the effect of film thickness of copper phthalocyanine (CuPc) on improving fluorinated copper phthalocyanine (F16CuPc) thin film transistor (TFT) performance with an organic pn junction. Electron field-effect mobility is exponentially enhanced up to 2.0×10− 2 cm2 V−1 s−1 with increasing of CuPc film thickness, and then unchanged when the CuPc thickness is over the saturation thickness (3 monolayers). The charge carrier density at the interface of F16CuPc/CuPc decreases the total TFT resistance, which leads to the increase of mobility. Threshold voltage is suppressed with increasing CuPc films. On the other hand, larger current on/off ratio is obtained when islanded CuPc films are formed on the surface of F16CuPc films. Therefore, employing an organic pn junction is an effective and simple method to fabricate high performance of n-channel transistors for practical applications. [Copyright &y& Elsevier]

Pentacene thin film transistors were fabricated and characterized with PVA thin films as a gate dielectric. The maximum process temperature was 70°C, which corresponds to a baking temperature of the spin-coated polymeric dielectric. Glass and flexible PET foils were used as substrates. Theses devices showed high performance electrical characteristics and worked at a low operating voltage of - 5 V. The highest field effect mobility of 2.6 cm2/Vs and the lowest threshold voltage of - 1.7 V were obtained on a flexible substrate. [ABSTRACT FROM AUTHOR]

The effects of O2 and H2O on the electrical characteristics of pentacene thin film transistors have been investigated using in situ and ex situ I–V measurements. We found that O2 enhances the saturation current by about 10%, and the mobility is only slightly increased. The effect of H2O on the device performance is considerably complicated. The physically absorbed water degrades the device performance, and the chemically absorbed water interacts with pentacene to form pentacene/(H2O)n clusters, which enhance the saturation current. On the other hand, the effect of H2O is found to be partly reversible after repumping to vacuum due to the undissociated clusters, which attribute to the variations of the saturation current and field effect mobility. [Copyright &y& Elsevier]

Abstract: Ambipolar organic thin-film transistors (OTFTs) was fabricated with heterostructure of thin films of fluorinated copper phthalocyanine (F16CuPc) and α,α′-dihexylsexithiophene (DH-α6T). The heterostructure TFT showed highly air-stable ambipolar characteristics with their hole and electron field-effect mobilities of 1.77×10−3 cm2/Vs and 8.18×10−3 cm2/Vs, respectively. Finally, complementary CMOS-like inverters comprising two ambipolar OTFTs were constructed. [Copyright &y& Elsevier]

Ambipolar organic thin-film transistors (TFTs) based on a fluorinated copper phthalocyanine (F16CuPc)/copper phthalocyanine (CuPc) homostructure layer were fabricated and characterized. The homostructure TFTs showed typical air-stable ambipolar characteristics, with hole and electron mobilities of 1.44×10-3 and 9.97×10-4 cm2/V s, respectively, which are comparable to unipolar mobilities in these single-layer devices. X-ray diffraction analysis suggests highly ordered F16CuPc and CuPc polycrystalline thin films could be continuously grown via an intermediate-phase layer in the homostructure. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the density of pn-heterojunction interface states by evaluating the threshold voltage shift with in-situ measurement of electrical characteristics of a sandwich fluorinated copper phthalocyanine/pentacene thin film transistor with various thicknesses of pentacene thin films. A threshold voltage (VT ) undergoes a significant shift from +20.6 to +0.53V with increasing the thickness of pentacene. When the thickness of pentacene is more than a critical thickness of 15nm, VT undergoes hardly any shift. On the other hand, the value of mobility is lightly decreased with increasing the thickness of pentacene due to the effect of the bulk current. Thus the VT shift is attributed to the increase of drain current in the sandwich device. In order to explain the VT shift, a model was assumed in the linear region of thin film transistor operation and the VT shift agrees with a tan−1 function of film thickness. The total charge density (Q 0) of 1.53×10−7 C/cm2 (9.56×1011 electrons or holes/cm2) was obtained. Furthermore, the VT shift and Q 0 could be adjusted by selecting a p-type semiconductor. [ABSTRACT FROM AUTHOR]